depends on the year of sx500r. i had damn near everything done to mine that could be done. here is the list;
-mbrp trail can (twin pipes too finicky)
-reed stopper notch (improves starting and makes sled snappyer)
-vmaxjhons clutchung from the tec pages (very worth it)
-engine torque limiter
the rest of the mods where for the chassis/handleing.
-121" 1-1/4" camoplast ripsaw
-ice scratchers
-02 viper skis
-srx rear heat exchanger
-cb performance front end kit (best one yet)
-putting the 1999 sx500r gearing in. 00-01 was dropped one tooth on the top so it only did 80mph before i fixed it.
great little sled that i still miss some times in the twistys as it handled like it was on rails. only mod that i had left to do to it was porting and maybe a big bore but i was undecided on that.